The life and operation of sensitive loads, such as devices containing LED luminaires, are negatively affected by power quality issues such as sag, swell, flicker, etc. Auxiliary power systems, such as a standby generator, can mitigate the impact of power interruptions, but do not resolve power quality issues. Uninterruptable power supply (UPS) systems can mitigate power quality issues, but have several drawbacks. As an example, a UPS system such as disclosed in U.S. Pat. No. 7,142,950 has no added value when there are no power issues. As another example, UPS systems are typically arranged for mitigating power interruptions and are therefore over dimensioned for mitigating power quality issues.